The goal of this project is to improve the clinical performance of dental amalgam by gathering information which can serve as a basis for the rational modification of amalgam systems. The primary scientific discipline involved will be metallurgy. Since the performance of a metal alloy is specifically related to its microstructure, the following procedure will be utilized. Microstructural features will be related to laboratory tests which are considered to be most relevant to clinical performance. In addition, methods to modify microstructure will be determined so that optimized configurations can be achieved. Microstructural determinations will be performed using an electron probe microanalyzer, optical metallography and X-ray diffraction. Laboratory tests will include impact strength, transverse strength and modulus of elasticity, transverse and static creep, anodic polarization and other electrochemical tests. The clinical performance factors of marginal fracture, corrosion, microleakage and Hg vapor emission will receive special emphasis. In view of the predominant role played by amalgam in the restoration of carious posterior teeth, even minor improvements in this material can produce very significant oral health benefits.